Skip to main content

How should we treat virtual methods exposed in APIs (Part 2)

In postul precedent am descutat despre o problema care poate sa apara cand expunem intr-un API metode virtuale, care sunt apoi suprascrise de catre un alt dezvoltator. Iar o versiune ulterioara a API schimba comportamentul aplicatiei in asa fel incat suntem obligati sa schimbam codul care foloseste API expus.
Mai jos gasiti o posibila solutie la aceasta problema.
public abstract class FooBase
{
private void DoAction()
{
// Custom code that can be executed by our method.
DoActionCore();
// More custom code that can be executed by our method.
}

public virtual void DoActionCore()
{
// Some action
}
}

public class MyCustomFoo : FooBase
{
public override void DoActionCore()
{
// My custom code of MyCustomFoo that will be
// executed by DoAction method from base class.
}
}
O solutie de acest gen o sa functioneze, doar daca cel care expune API o sa o foloseasca de la prima versiune.
O alta varianta este ca metode DoActionCore sa fie declarata ca si abstracta, in cazul in care vrem sa obligam dezvoltatorul sa defineasca un comportament custom.

Comments

  1. Presupui ca atunci cind un API este creat intr-un anumit fel, el este imutabil pentru ca exista deja third party-uri care il folosesc. Dar de fapt imutabilitatea aceasta nu preclude existenta unei alte variante de API care sa faca ce trebuie.

    In alte cuvinte nu sint de acord cu ideea ca ceva merge doar daca s-a gindit cineva inainte la asta. Orice design trebuie sa fie adaptabil, iar asta este singura responsabilitate a dezvoltatorului: sa il faca astfel.

    ReplyDelete
  2. Solutia asta are si un nume - template method pattern (http://en.wikipedia.org/wiki/Template_method_pattern).

    E ok ca si metoda de a permite customizarea behaviour-ului unei clase cat timp nu apar ierarhii de clase pe mai mult de 2 nivele, si cat timp nu apare necesitatea ca pentru o singura metoda din clasa de baza sa se ofere mai multe puncte de extensie - in ambele cazuri template method (foarte folosit cu ceva ani in urma) duce la cod greu de inteles si de intretinut.

    ReplyDelete
    Replies
    1. Mersi Tudor ca acum pot sa pun titlu la un sablon pe care il cunosteam si foloseam ;)

      Delete
    2. :) e doar o conventie - si eu il foloseam cu 10 ani in urma si nu stiam cum l-au botezat..

      Delete

Post a Comment

Popular posts from this blog

Windows Docker Containers can make WIN32 API calls, use COM and ASP.NET WebForms

After the last post , I received two interesting questions related to Docker and Windows. People were interested if we do Win32 API calls from a Docker container and if there is support for COM. WIN32 Support To test calls to WIN32 API, let’s try to populate SYSTEM_INFO class. [StructLayout(LayoutKind.Sequential)] public struct SYSTEM_INFO { public uint dwOemId; public uint dwPageSize; public uint lpMinimumApplicationAddress; public uint lpMaximumApplicationAddress; public uint dwActiveProcessorMask; public uint dwNumberOfProcessors; public uint dwProcessorType; public uint dwAllocationGranularity; public uint dwProcessorLevel; public uint dwProcessorRevision; } ... [DllImport("kernel32")] static extern void GetSystemInfo(ref SYSTEM_INFO pSI); ... SYSTEM_INFO pSI = new SYSTEM_INFO(

Azure AD and AWS Cognito side-by-side

In the last few weeks, I was involved in multiple opportunities on Microsoft Azure and Amazon, where we had to analyse AWS Cognito, Azure AD and other solutions that are available on the market. I decided to consolidate in one post all features and differences that I identified for both of them that we should need to take into account. Take into account that Azure AD is an identity and access management services well integrated with Microsoft stack. In comparison, AWS Cognito is just a user sign-up, sign-in and access control and nothing more. The focus is not on the main features, is more on small things that can make a difference when you want to decide where we want to store and manage our users.  This information might be useful in the future when we need to decide where we want to keep and manage our users.  Feature Azure AD (B2C, B2C) AWS Cognito Access token lifetime Default 1h – the value is configurable 1h – cannot be modified

What to do when you hit the throughput limits of Azure Storage (Blobs)

In this post we will talk about how we can detect when we hit a throughput limit of Azure Storage and what we can do in that moment. Context If we take a look on Scalability Targets of Azure Storage ( https://azure.microsoft.com/en-us/documentation/articles/storage-scalability-targets/ ) we will observe that the limits are prety high. But, based on our business logic we can end up at this limits. If you create a system that is hitted by a high number of device, you can hit easily the total number of requests rate that can be done on a Storage Account. This limits on Azure is 20.000 IOPS (entities or messages per second) where (and this is very important) the size of the request is 1KB. Normally, if you make a load tests where 20.000 clients will hit different blobs storages from the same Azure Storage Account, this limits can be reached. How we can detect this problem? From client, we can detect that this limits was reached based on the HTTP error code that is returned by HTTP